In a large stock pot add a little oil and fry off the onion. Add the vegetable stock concentrate and other vegetables as well as the chicken carcass. To that add at least 10 cups of water. Boil everything for at least an hour (lid on) until the chicken bones are collapsing. Remove the bones and when cooled, pick off the meat and add back into the pot. You will need to add a few more cups of water to bring the level of the soup up again. Season to taste with salt and pepper. Add the risoni and cook until al dente.

Serve with crusty bread.